Poly(arylene sulfide ketone), henceforth abbreviated as PASK, and poly(arylene sulfide diketone), henceforth abbreviated as PASDK, resins are engineering thermoplastics of potential commercial interest for film, fiber, molding, and/or composite applications because of their outstanding thermal and mechanical properties. General processes for the production of PASK and PASDK are known in the art. For example, PASK and PASDK can be prepared by the reaction of an alkali metal sulfide in a polar organic compound with a polyhaloaromatic ketone or a polyhaloaromatic diketone, respectively.
Disadvantages often associated with the production of PASK and PASDK resins pertain to the processability and the thermal stability of the polymers produced. Specifically, at the completion of a typical polymerization reaction, the reaction mixture is generally in the form of a slurry comprising a liquid phase (predominantly a polar organic compound and water) and a particulate phase (predominantly polymeric resin), wherein the polymeric resin contained in the particulate phase is in the form of powder-like particles when recovered. These powder-like polymeric particles have very low bulk densities when recovered (e.g., generally less than 10 lbs/ft.sup.3). The slurry containing this extremely fine powder-like resin filters very slowly and, thus, hampers the polymer's washability, recoverability and processability. Washing, recovering and/or processing PASK and PASDK resins which have low bulk densities are extremely difficult.
Other problems which are inherent with low bulk density resins pertain to commercial plant operations, such as production and storage capacities and/or environmental concerns. Specifically, since production and storage vessels in a commercial plant have a constant volume associated therewith, as the bulk density of a polymeric resin decreases, so does the production and storage capacity of the commercial plant. Therefore, if the bulk density of a polymeric resin can be increased, the production and storage capacities of the commercial plant would also increase.
As for environmental concerns, a low bulk density resin which is in the form of a powder would have a greater tendency of being dispersed through the air of the working environment during downstream processing and handling procedures than would a similar polymeric resin having a higher bulk density. Therefore, providing a polymeric resin having an increased bulk density would improve the environmental conditions which are associated with the handling and processing of such a resin.
Although in some commercial applications it is desirable to have the PASK or PASDK resin in the form a fine powder, in many other commercial applications, having a PASK or PASDK resin which has associated therewith higher bulk densities would be commercially desirable for the reasons stated above.
As stated earlier, another disadvantage associated with the preparation of PASK and PASDK resins pertains to the resins' thermal stability. Specifically, PASK and PASDK resins generally have relatively low thermal stabilities. When either PASK or PASDK resins are prepared and recovered by conventional methods, the resins contain certain volatile by-product materials. Since many polymer processing procedures (e.g., melt-forming, extrusion and blow-molding) require that the resin be heated to a temperature above its melting point, and since both PASK and PASDK resins have melting points above about 315.degree. C. (600.degree. F.), the subsequent melt-processing of PASK and PASDK resins can result in these volatiles vaporizing and/or boiling through the polymeric resin, often leaving voids therethrough. This vaporization of volatile materials is commonly known in the polymer industry as "degassing" and/or "out-gassing". One detrimental effect of this degassing phenomena can be that of decreasing the melt stability of the PASK and PASDK resins. Since high melt stability is a necessary characteristic of resins which are to be melt processed, a low melt stability makes melt-processing procedures very difficult.
Melt-processing PASK or PASDK resins in a manner which results in a substantially void-free product has many inherent commercial applications. Therefore, it would be most desirable to produce melt stable PASK and PASDK resins of good polymer quality.
The internal pressures in polymerization process vessels during typical polymerization reactions are generally high (e.g., above about 150 psig). Safety risks and economic concerns are often associated with excessively high polymerization reactor pressures. For instance, as the internal pressure of a polymerization process vessel increases, the risk of potential safety hazards increases, as does the cost of designing and/or fabricating this process vessel.
When designing, purchasing and/or fabricating polymerization process vessels, one does so with the understanding that the polymerization process for which it will be employed will generate pressures falling with a specific range. Therefore, although a process to provide higher bulk density PASK or PASDK resins which have associated therewith improved thermal stability and improved processability is desirable, the desirability of such a process may decrease if it results in generating pressures within a polymerization process vessel which were in excess of the vessel's operable range.